Impact and explosive force minimization structures

ABSTRACT

A helmet including an insert provides the ability of including a highly energy absorbing feature within the insert. The insert includes a structure such as a Bingham plastic which, upon impact, absorbs the energy of the impact by converting from a solid to a liquid. Other energy absorbing features are contemplated. The energy absorption process occurs in one aspect in a nonreversible manner such that once a high enough level impact occurs on the insert, it must be replaced within the helmet. The insert has a fastener which enables it to be replaceable. In this manner, a highly absorbing feature of a helmet can be provided to reduce concussions while not requiring the complete replacement of a helmet.

PRIORITY INFORMATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/912,343, filed 5 Dec. 2013, U.S. Provisional Patent ApplicationNo. 62/047,976, filed 9 Sep. 2014, and U.S. Provisional PatentApplication No. 62/016,337, filed 24 Jun. 2014. This application is acontinuation-in-part of U.S. Non-Provisional patent application Ser. No.13/267,519, filed 6 Oct. 2011, which claims priority to U.S. ProvisionalPatent Application No. 61/442,469, filed 14 Feb. 2011. This applicationis a continuation-in-part of U.S. Non-Provisional patent applicationSer. No. 13/267,551, filed 6 Oct. 2011, which claims priority to U.S.Provisional Patent Application No. 61/442,469, filed 14 Feb. 2011. Thisapplication is a continuation-in-part of U.S. Non-Provisional patentapplication Ser. No. 13/267,590, filed 6 Oct. 2011, which claimspriority to U.S. Provisional Patent Application No. 61/442,469, filed 14Feb. 2011. This application is a continuation-in-part of U.S.Non-Provisional patent application Ser. No. 13/267,604, filed 6 Oct.2011, which claims priority to U.S. Provisional Patent Application No.61/442,469, filed 14 Feb. 2011. This application is acontinuation-in-part of U.S. Non-Provisional patent application Ser. No.14/139,012, filed 23 Dec. 2013, which is a continuation-in-part of Ser.No. 13/267,604, filed 6 Oct. 2011, which claims priority to U.S.Provisional Patent Application No. 61/442,469, filed 14 Feb. 2011, thecontents of which applications are herein incorporated by reference intheir entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to impact minimization structures such ashelmets, blast walls, protective clothing, helmets, vehicle protectionand so forth. The structures incorporate in various methods andstructures that use of Bingham plastics, low modulus rubbers, auxeticand structural textiles, incorporated into dissipative and/orsequentially dissipative devices and/or other mechanisms and materialsto protect individuals and structures from percussive forces andbludgeoning damage.

2. Introduction

Most protective equipment is designed for protection against penetratingforce and piercing damage. Armors act to blunt penetrating force, thuspreventing catastrophic piercing damage. Unfortunately, many commonthreats to individuals and structures come from percussive (compressionwave) force. In contrast with penetrating force which rapidly transfershigh energy to create focused, piercing damage, percussive impactstransfer large quantities of total energy from lower energy waves at arelatively long rate of transfer resulting in accumulated bludgeoningdamage. There is currently a need for improved protective technologytargeted to percussive impact and dissipating bludgeoning damage. Forexample, helmets are used by football players, bike riders, skaters,military applications, and so forth. However, the rate of concussioninjury is still high. Similarly, other protective gear is used in manydifferent areas. Military personnel and vehicles need improvedprotection against impacts of various kinds. It is desirable to improvepercussive damage protection technology.

Helmets and other armors are designed to reduce individual damage.Piercing damage is a common result of a transmission of penetratingforce, with high peak energy delivered rapidly to a small area. Theresults of penetrating force are slicing injuries. Reductions inpenetrating force can be generally achieved by designs that widen theimpact zone to prevent penetration, including those of the technologiesdescribed herein. Bludgeoning damage is a common result of atransmitting percussive force, with low peak energy delivered slowly toa large area. The results of percussive force are crushing damage totissue, concussions or other injuries affecting a broad area. Reductionsin percussive force are not amenable to traditional design, and requirespecial attention through designs that dissipate the energy using thedescribed technology.

In other cases, an impact device, in particular of a percussive design,might be also placed near a building and there is a need to protect thebuilding and occupants from the damage caused by the blast, inparticular of a bludgeoning type. There also is a need for structuresusing the described technologies to help prevent or reduce the effectsof a blast on buildings or other object.

SUMMARY

Additional features and advantages of the disclosure will be set forthin the description which follows, and in part will be understood fromthe description, or can be learned by practice of the herein disclosedprinciples. The features and advantages of the disclosure can berealized and obtained by means of the instruments and combinationsparticularly pointed out in the appended claims. These and otherfeatures of the disclosure will become more fully apparent from thefollowing description and appended claims, or can be learned by thepractice of the principles set forth herein.

The present disclosure includes various embodiments related tostructures for protecting individuals from different kinds of impact.One embodiment applies to a helmet used for football. Other helmetembodiments cover bike helmets, motorcycle helmets, or other kinds ofhelmets. Other personal protective armor embodiments cover body armor.Other protective armor embodiments cover moving vehicles. Anotherembodiment applies to a tent wall used to protect a building. Acontainer or a blast blanket can also be used with the principlesdisclosed herein. Other embodiments encompass blast walls built intobuildings, or other structures. Other embodiments encompass flexiblewalls to protect vehicles. Generally, the principles disclosed hereindescribe the uses of: a Bingham plastic or similar material that convertfrom a solid to a liquid upon experiencing a threshold force; moderatemodulus rubber that displace laterally upon experiencing a thresholdforce; textiles that rupture upon experiencing a threshold force; foamsthat expand upon experiencing a threshold force. These embodimentsinclude the use of such materials individually, in stacks and/or incombination to optimize dissipation of low peak energy, broadlydistributed energetic impacts.

A first embodiment includes a helmet having a shell with an innersurface. A first component includes a fastener attached to the innersurface. The first component can be part of a fastener, a snap, orVelcro. An insert is made at least in part from a plastic and has asecond component of the fastener attached to the plastic. The secondcomponent can be the opposing component of a snap, Velcro, or otherfastening mechanism. The insert is removable by separating a connectionbetween the first component and the second component. The plastic canbe, for example, a Bingham Plastic that changes from a solid to a liquidat a shear threshold such as particular force being applied to thehelmet. Upon the force being applied, the plastic converts to a liquidand absorbs at least some of the energy of the force or the impact. Thisreduces the amount of energy transferred to the head of the individual,thus reducing the probability of a concussion or other injury.

In the first embodiment, the Bingham plastic can be a mixture ofpolyvinyl alcohol, water and borax at concentrations to provide targetthreshold energy. The plastic can include, for example, between 2% and20% of hydrolyzed polyvinyl alcohol and between 0.5 and 8% borax. Inother embodiments, the Bingham plastic can be any mixture of a plastic,e.g. polyacrylic acid, guar gum water soluble plastics, polyacrylate andpolynitrile hydrocarbon soluble plastics, capable of inter- andintra-chain interactions, dissolved in an appropriate miscible solvent,with temporary or permanent cross-linking chemistry or additive agentsto provide target threshold energy.

In a second embodiment, the plastic can also be, for example, a gradedfoam that expands laterally rather than compressing under applied load.Upon the force being applied, the plastic displaces laterally to absorbenergy without displacement of the inner surface of the insert relativeto the surface of the head as significantly or at all. This reduces theamount of energy transferred to the head of the individual, thusreducing the probability of injury. The structure of the graded foam canbe triangular, circular, rectangular, or any other shape.

In the second embodiment, the graded foam can be a graded combination ofpolyurethane foams with different mechanical modulus to provide a targetrange of deformation threshold energies. In other embodiments the targetrange can be achieved using polyurethanes of different chemical orphysical densities. In other embodiments, the target range can beachieved using polyurethanes with different physical or chemicaldensities or modulus combined with nanoparticulates and/ormicroparticulates of silica. In other embodiments the particulates areother ceramic, metal or plastics. In other embodiments, the plastic canbe other flexible foam material, e.g. foamed styrene butadiene rubbers,styrene-butadiene-styrene rubber, or co-polyesters, co-polyamides, orco-polyacrylates.

In a third embodiment, the plastic can also be, for example, a rubberwith a low modulus that displaces laterally at a shear threshold. Uponthe force being applied the material displaces laterally and slowing thetransfer of shear energy rather than allowing shearing energy to betransferred rapidly to the surface below. This reduces the peak energytransferred to the head of the individual, thus reducing the probabilityof injury.

In the third embodiment, the rubber can be a Plastisol or plasticizedpolyvinyl chloride plastic. In other embodiments the rubbery elasticplastic can be any type of plastic that can be formulated or chemicallymanipulated to produce a target shear modulus, e.g. Kraton or otherstyrene/butadiene copolymers, natural rubber and polyisoprene, andpolysilane (silicone) rubber. In another embodiment, the rubber can becomprised of layers with differing shear moduli. The rubber can beutilized on an insert, on an inner surface of a helmet, wall, blastblanket or other structure, or on an outer surface of the helmet, wall,blast blanket or other structure.

In a fourth embodiment, the plastic can be a cotton fabric layer that isstructured such that the yarn will break on the application of a shearthreshold. Upon the force being applied the yarn tears and ruptures soas to consume energy in breaking. This reduces the peak energytransferred to the surface of the structure or individual, thus reducingthe probability of damage or injury. In another embodiment the yarn canbe comprised of an appropriate chemistry and diameter to have a targetfailure threshold, e.g. polyester, nylon, or glass.

In fifth embodiment, the fabric layer can be a helical-auxetic, yarnthat becomes thicker as it extends and prevents percussive force frompenetrating deeper as the fabric structure becomes more porous. Inanother embodiment, the auxetic yarn can have different structure orchemistry that causes the yarn to become thicker as it extends whenunder tension. In a sixth embodiment, the fabric layer can be a textilewith loops of cotton yarn woven in such a way as to form 1 inch loopsthat are connected with yarns of a lower modulus such that underpercussive force and the resulting extension will break and allow thefabric to expand before breaking again. In another embodiment the fabriclayer can use loose weaves that take a zig-zag or other pattern thatallows expansion.

In a seventh embodiment the layer can be a plate composed of one or moretypes combinations of the Bingham plastic, rubbery elastic plastic orfoam plastics of the first, second and third embodiments or otherembodiments and arranged in a fish-scale pattern. In another embodimentthe plates overlap in other patterns. In another embodiment, the platescan be arranged such that the plates are contiguous and butt againsteach other. In another embodiment the plates can be arranged that theplates are non-contiguous and are placed so as to optimize theinteraction with an impacting force. In another embodiment the textilecan be an ordinary textile.

In an eighth embodiment, the insert is removable. A removable insert foruse in a helmet includes a plastic that changes from a solid to a liquidat a shear threshold. A first component of a faster is attached to theplastic. The first component of the fastener connects to a secondcomponent of the fastener, and the second component is attached to thehelmet. The insert can one or more layers, each having a differentstructure as disclosed herein. For example, one layer may be oftriangular graded foam, with another layer including a plastisol, and athird layer including a Bingham Plastic.

In a ninth embodiment, a plastisol plastic or other low to moderaterubber material layer of embodiment three is attached to the outersurface of the helmet. In this embodiment, a helmet includes a shellhaving an outer surface and a plastisol layer attached to a portion ofthe outer surface. The plastisol plastic layer can also be positioned onan inner surface of the helmet or as part of a removable insert.

In another embodiment, a removable insert for use in a helmet, whereinthe removable insert includes a first layer having first plastic thatchanges from a solid to a liquid at a shear threshold, the first plasticbeing a first color, the first layer having first component of afastener attached thereto. The first component of the fastener connectsto a second component of the fastener, the second component beingattached to an interior surface of the helmet. A second layer has asecond plastic that changes from a solid to a liquid at the shearthreshold, the second plastic being a second color, the second layerbeing adjacent to the first layer. Upon the removable insert beingimpacted at the shear threshold, the first layer mixes with the secondlayer to reveal the first color. In this manner, if an impact isexperienced that is at or above the shear threshold, the user can lookat the insert. If, for example, the first color is red and the secondcolor is white, then the insert would have some red showing which wouldindicate that the insert has absorbed the impact and should be replaced.

In another embodiment, a removable insert for use in a helmet, whereinthe removable insert includes a first layer having first rubbery plasticthat displaces at a shear threshold, the first plastic being a firstcolor, the first layer having first component of a fastener attachedthereto. The first component of the fastener connects to a secondcomponent of the fastener, the second component being attached to aninterior surface of the helmet. A second layer has a second plastic thatdeforms at the shear threshold, the second plastic being a second color,the second layer being adjacent to the first layer. Upon the removableinsert being impacted at the shear threshold, the second layer deformsto expose the first layer to reveal the first color. In this manner, ifan impact is experienced that is at or above the shear threshold thatdamages the first layer, the user can look at the insert. If, forexample, the first color is red and the second color is white, then theinsert would have some red showing which would indicate that the inserthas absorbed the impact and should be replaced.

The present disclosure also relates to a cartridge or insert that can beformed to fit within a helmet or other larger enclosure. The cartridgepreferably is structured such that it can be positioned within a helmetin a location that is most likely to receive a hard hit. For example,typically, the forehead area of a helmet is the area that will receivethe most force and the most common area where hits occur on a footballplayer's helmet. The present disclosure relates to providing a removablecartridge which covers this high impact area and which can include animproved structure for absorbing the energy of an impact. For example,in one embodiment, Bingham plastics are used within the cartridge whichcan dissipate the energy received from an impact by converting theBingham plastic from a solid to a viscous fluid. Bingham plasticrepresents a viscoplastic material that in a natural state is a rigidbody but at a particular level of stress can convert and flow into aviscous fluid.

The present disclosure also relates to a cartridge or attachment thatcan be formed on the external surface or a helmet or other smallerenclosure. The rest of the disclosure is identical to that describedabove.

In a case where an impact causes a Bingham plastic to convert from asolid to a fluid, the change may be irreversible. Accordingly, the basicembodiment of this disclosure includes a cartridge having Binghamplastic such that when an impact of a certain level of stress occurs onthe cartridge, the Bingham plastic converts from a body into a viscousor Newtonian fluid, and causes the plastic to flow into a reservoir orsome other location. At this point, the value of the cartridge isreduced because the Bingham plastic has become distorted, and therefore,the cartridge must be replaced. The present disclosure relates tosystems and methods related to such cartridges or inserts.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the disclosure can be obtained, a moreparticular description of the principles briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only exemplary embodiments of the disclosure and are nottherefore to be considered to be limiting of its scope, the principlesherein are described and explained with additional specificity anddetail through the use of the accompanying drawings in which:

FIG. 1 illustrates a prior art football helmet;

FIG. 2 illustrates various inserts according to an embodiment of thisdisclosure;

FIG. 3 illustrates several variations of the structure of the inserts;

FIG. 4 illustrates an embodiment including an electronic component fortransmitting a signal associated with an impact to a remote device;

FIG. 5 illustrates an embodiment including an electronic component thatcommunicates with another electronic component within the helmet forsignaling an impact;

FIG. 6 illustrates example shapes of the inserts for use in a helmet;

FIG. 7 illustrates various structures that can be used for the inserts;

FIG. 8 illustrates another embodiment having a plastic layer between theshell and the fastener for the insert;

FIG. 9 illustrates a plastic outer surface to the shell of a helmet;

FIG. 10 illustrates an alternate approach to the plastic outer surfaceof the shell of the helmet;

FIG. 11 illustrates a cartridge embodiment;

FIG. 12 illustrates an alternate approach to the cartridge embodiment;

FIG. 13 illustrates the layering approach to an embodiment;

FIG. 14A illustrates an embodiment wherein the plastic layer hasmultiple layers which mix upon the threshold shear impact beingexperienced to change a color of the insert and provide notice of theimpact;

FIG. 14B illustrates the change in color of one or more inserts;

FIG. 15 illustrates a method embodiment;

FIG. 16 illustrates zones within the helmet;

FIG. 17 illustrates transmission of load upon contact;

FIG. 18 illustrates a graded foam structure or layer;

FIG. 19 illustrates several features of this disclosure with respect ablast shock wave and protecting buildings;

FIG. 20 illustrates building a blast layer surface around an explosivedevice; and

FIG. 21 illustrates various potential layers for a blast surface.

DETAILED DESCRIPTION

Various embodiments of the disclosure are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustration purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without parting from the spirit and scope of the disclosure.

The general focus of this disclosure is impact resistant/absorbingstructures. These structures can have various forms. Disclosed hereinare several embodiments of impact resistant/absorbing structures rangingfrom helmet technologies to blast surface layers that can be constructedaround an explosive device to contain the explosion or as a wall placednear an explosive device to protect individuals or materials on theother side of the wall from the effects of an explosion. The principlesdisclosed herein describe the uses of: (1) a Bingham plastic or similarmaterial that convert from a solid to a liquid upon experiencing athreshold force; moderate or low modulus rubber that displace laterallyupon experiencing a threshold force; (2) plastisol materials; (3)textiles that rupture upon experiencing a threshold force; and (4) foamsand foam structures that expand upon experiencing a threshold force.These embodiments include the use of such materials individually, instacks and/or in combination, to improve the dissipation of low peakenergy, broadly distributed energetic impacts.

The disclosure begins with helmet technology and various componentsrelated to helmet technology such as the use of plastisols (or other lowto moderate rubber material) and Bingham Plastics, including fiberreinforcement, to reduce injury such as concussions. Following thediscussion on various helmet embodiments, this disclosure will focus onblast containment layers associated with walls and other structures.

The helmet embodiment includes several separate aspects for reducing theimpact on the user. The first is use of Bingham Plastics made from asolution of vinyl alcohol (PVA) and water and cross-linked with sodiumtetraborate (borax). Natural and synthetic fibers can also be combinedwith the Bingham Plastic to increase the effectiveness. The BinghamPlastics are preferably used on inserts or cartridges that are removablepositioned inside the helmet or as part of the surface of the helmet.Example lengths of the natural or synthetic fibers include 0.5-5 cm inlength. The fibers included in the plastic can also include variouslength of fibers and a combination of both natural and synthetic. Forexample, the plastic could contain 20% natural fiber with lengths at 1-2cm and 80% synthetic fibers having lengths between 2-4 cm. Anycombination of percentages and lengths are contemplated herein.

The Bingham plastic can be any mixture of a plastic, e.g. polyacrylicacid, guar gum water soluble plastics, polyacrylate and polynitrilehydrocarbon soluble plastics, capable of inter- and intra-chaininteractions, dissolved in an appropriate miscible solvent, withtemporary or permanent cross-linking chemistry or additive agents toprovide target threshold energy.

In another aspect, plastisols are used as an additional layer on theouter surface of the helmet to reduce the effect of an impact. Theplastisol layer can have a single or multiple layer configurations. Thediscussion below regarding the helmet embodiment covers both aspects ofprotection.

Discussion of the Study of Bingham Plastics

Next the disclosure discusses various studies and information related tothe development of Bingham Plastics for the purposes of preventingconcussions or other injuries.

The following Chart 1 illustrates example mixtures with respect to howto make the required Bingham plastics (PVA/borax) samples for the energydissipation gels using 99% hydrolyzed Poly(vinyl alcohol) (PVA), sodiumtetraborate (Borax) and water.

CHART 1 PVA (%) Borax (%) ID 4 2 and 8 4/2 or 4/8 6 8 6/8 12 2 and 812/2 or 12/8 16 2 and 8 16/2 or 16/8

An example procedure of creating the Bingham plastic is to fill acontainer with water and add the appropriate amount of PVA of the volumeof water in the container (e.g. for 1000 grams of water, add 40 grams ofPVA to make a 4% solution) to create or yield a solution. The solutioncan be baked at 250 F until the solution appears clear (non-cloudy).Note that depending on the volume and concentration of the solution, thebake time will the longer.

There may be a dry skin-like film on the surface of some of thesolutions after about an hour, depending on the volume. This can beremoved and the heating continued until the solution clears. Borax canthen be poured into the PVA solution and mixed. The greater theconcentrations of PVA and borax, the more difficult it may be to stir.This step yields a mixture.

The mixture can be heated in an oven at 250 F. Stirring the mixture atabout 5 minutes intervals yields a gel-like substance. Higherconcentrated PVA solution can take a longer time in the oven tocompletely dissolve. Also the larger the volume of the solution is, thelonger it will take to completely dissolve.

The gel-like substance can be packed into plastic bags and sealed airtight. Exposure of the gel to the atmosphere will cause the PVA andBorax mixtures to dry out and lose desirable properties, thus ispreferably avoided by sealing in an air tight package. This processyields the Bingham Plastic layer associated with an insert in thehelmet. The plastic includes between 2% and 20% of hydrolyzed polyvinylalcohol and between 0.5 and 8% borax.

Prototype helmets were fabricated to demonstrate the materials in placeon an actual football helmet. Standard football helmets were purchasedas the base system. Several Schutt XP Hybrid helmets were procured. Theinterior padding of the Schutt Helmet was replaced. Bingham plastics asdescribed above can be prepared and used to replace the standard foaminserts. There are two basic standard foam insert configurations—thefoam itself and the white pad/support systems.

The foam is about 3 cm thick and is attached to the interior of thehelmet using velcro fasteners. To replace the foam inserts, 16/8 Binghamplastics were produced and formed to shape in small polyethylenepackages to approximate the original shape of the foam inserts. Rememberthat 16/8 means the percentage of PVA and Borax. These do not have to beexact percentages. For example, a range of PVA can be between 1 and 30%and the percent of Borax can be between 0.5 and 20. Any combination ofthese percentages is contemplated within this disclosure. The air tightpackets containing the mixture were adhered to a felt backing. Thebacking can attach to the existing Velcro fasteners in the helmet.

The white pad/support system from the standard helmet includes, by wayof example and not limited to a particular thickness, a 1 cm thick foamcontained in a vinyl wrapper and supported by a plastic pyramid crushsystem. The foam is very soft as it comes in contact with the ears. A4/2 Bingham plastic was put into an airtight polyethylene packet andattached to the existing support system. The systems (inserts) snap intoplace in the helmet as is shown in FIG. 2. The choice of the 4/2 balanceof PVA and Borax was to keep the very low compressive stiffness of theoriginal foam. Using this system, it is possible to switch the prototypehelmet from original padding to the substitute material with ease.

Impact testing was performed on the samples having Bingham Plasticinserts for both perpendicular compressive impact at 100 Joules and 33Joules, and oblique shear impact at 100 Joules. Samples of Binghamplastics were produced using a solution of poly(vinyl alcohol) (PVA) andwater, cross-linked using sodium tetraborate (borax). In some cases, theresult was plastics having gel-like properties as described when theBingham Plastic is prepared by the process described above. Thematerials were produced from different concentrations of 99% hydrolyzedPVA, at concentrations of 4%, 6%, 12% and 16% by weight. Borax was addedto these solutions at weight fractions of 2%, 4% and 8% to get differentstiffness materials with different shear yield thresholds. Differentconcentrations of PVA (reported as weight percent in water) wereproduced, and for the different concentrations, different amounts ofborax were added (reported as weight percent of water). Seven differentconfigurations of PVA/Borax were produced and tested at differentthicknesses. Small quantities of pigment were added to the variousmixtures to make it easy to visually recognize the sample chemistry.

The materials were stored in air tight plastic bags (other materialscould be used as well) to minimize drying of the materials, and weretested while in these bags. The bags fit loosely in the testing. It iscontemplated that in an embodiment of the disclosure that the bags couldeither be loosely fit or tightly fit around the plastic such that thebags conform closely to the form of the plastic.

In one aspect, the bags or containers for the Bingham plastics can be ofany type of material that is appropriate for holding the Bingham plasticin place and for preventing flow of the Bingham plastic upon impact. Inanother aspect, a bag or outer container could have holes or openings orperforations that open at a threshold load which enable fluid toactually flow out of the bag upon impact. The perforation can becircular, or linear, or any other shape that can enable the container tobe air tight in normal use, but at a threshold value, the perforationwould tear and create an opening out of which the plastic in its liquidstate would exude. These containers could be composed of woven, knittedor non-woven textiles or made of a continuous, perforated film. Otherranges are contemplated as well for the percentages disclosed herein.Other types of Bingham plastic can be contemplated, for example thosecomposed of silicone oils, particles and polymers.

The various materials were subject to compression testing and impacttesting to determine their suitability for use. In one aspect, shortfibers (1-2 cm) can be combined with 4/2 PVA/Borax mixtures at a 5%weight fraction. Both natural fiber (jute) and synthetic fiber (PET)were added and the resulting samples were tested for 100 Joule impactresponse. The energy absorption was comparable to that of the 16/8samples. The 16/8 samples are the preferred embodiment. The naturalfiber samples performed slightly better than the synthetic fibersamples. The use of natural or synthetic fibers offers an inexpensiveroute to providing the desired energy absorbing properties. The shearmodulus and the compression modulus was tested and determined for thevarious samples. Other types of fillers are contemplated, includingdensity reducing materials such as microscopic glass or plastic balloonsor foamed Bingham Plastics. Any combination of ratios of percentages ofPVA and Borax, in connection with either natural or synthetic fibers ofvarious lengths, is contemplated.

Helmet prototypes were produced with removable inserts associated withBingham Plastics. A test was performed of the potential energy based onan impact towards a strike plate holding the sample under investigation.The potential energy of the strike plate after impact was measured andthe difference between the two was a measure of the absorbed energy bythe material receiving the strike. The test was performed initially withan approximately 3 kg strike plate and then again with an 8 kg strikeplate.

The compressive stress response was measured at relatively low loadlevels (up to 50 kPa for the stiffer materials, up to 7 kPa for thesofter materials) to extract the initial modulus and general behavior ofthe various Bingham plastics. Additionally, foam elements extracted fromfootball helmets were tested for comparison purposes.

The 4% PVA samples were tested in compression and showed a highsensitivity to the amount of borax. The compressive stiffness increasedwith more borax. Different elements of the football helmet were removed.In the interior of the helmet there were three different types ofpadding. The first material is a skinned foam (single piece of foam withhardened exterior), the ear pads and the top of the helmet are differenttypes of foam in a plastic envelope. The foam in the ear pad unitsconsists of a two-layer foam with a lower density foam on the ear sideand a higher density foam on the helmet side. The top pad has alow-density foam.

Impact testing was performed by releasing a 5.5 kg sphere withapproximately 35 or 100 Joules of potential energy towards a strikeplate holding the sample under investigation. The potential energy ofthe strike plate after impact was measured and the difference betweenthe two a measure of the absorbed energy by the material receiving thestrike.

The tests were performed with an 8.3 kg strike plate. A data loggingaccelerometer was attached to the strike plate. The acceleration of theplate due to impact was recorded. This was integrated to determine thevelocity as a function of time for the impact event, which typicallylasted for 0.02 to 0.04 seconds. The velocity of the strike plates afterimpact was calculated and the kinetic energy of the plate determined (½mv²).

Of interest is the energy dissipated by the target. This was calculatedby comparing the kinetic energy of the target without any sample on itto the kinetic energy when the samples are in place. The differencebetween the two represents the dissipation of energy from the samples.

In addition to using the accelerometer, high-speed video was captured ofthe events and the potential energy (mgΔh) in the strike plate wasmeasured at the peak of recoil.

Furthermore, the potential energy lost due to the support system wasmeasured and added back to the potential energy calculation from thevideo capture. The potential energy calculated from video measurementswas compared to the kinetic energy calculations from the accelerometer.The testing shows a correlation between the potential energy measurementfrom video capture and the kinetic energy measured from theaccelerometer. Samples were tested at three different thickness: 1, 2,and 3 centimeters. They were tested at two nominal impact levels: 35Joules and 100 Joules. The effects of different parameters can thus beextracted.

Not surprisingly, increasing the thickness of the sample increases theenergy dissipation and reduces the peak acceleration at impact. The peakacceleration was studied against part thickness for 100 Joule impact. Asthe part thickness increases, the peak acceleration decreases.

Looking at general trends with regards to chemistry, the effect of theamount of PVA and Borax in the Bingham plastic on the amount of energydissipated during impact was evaluated. For low energy impact (35 J)there is a slight increase in energy dissipation with increasing PVA forlow Borax content (2%) and a general decrease in energy dissipation withincreasing PVA for high Borax content (8%).

When considering the higher energy impact (100 J), the trend is forincreasing energy dissipation with increasing PVA concentrationregardless of the Borax content. The first pads from the Schutt helmetwere identified as the baseline material to meet or exceed inperformance. Because of the effect of thickness as noted above, and theneed for proper helmet fit, 3 cm thickness was identified as theappropriate sample thickness to use for comparison purposes. However, asnoted elsewhere in this disclosure, the thickness of any given insertcan vary from a small thickness such as 5 mm to a larger thickness suchas 5 cm, and even extend to thicknesses outside this range, such as lessthan 5 mm down to 1 mm and up to 10 cm.

In the study, the peak acceleration observed during impact for both 35and 100 Joule tests. For example, the 3 cm thick results showed thatbetter performance correlates with lower peak acceleration than thefirst pads from the Schutt helmet. At low energy impact, the 12/2, 12/8and 16/2 samples have a lower peak acceleration than the first pads,while 16/8 is very close in comparison. At high energy impact the 12/2,16/2 and 16/8 have lower peak acceleration than the first pads. 4/8 and12/8 have very similar peak accelerations.

A similar comparison can be made with the dissipated energy. This is theenergy that is absorbed by the sample and not transferred intomechanical energy of the strike plate. In this instance, the studylooked for materials that have higher dissipated energy than the orangepads, indicating that the materials has dissipated energy rather thantransferring it to the wearer of the helmet. The study showed that at alow energy (35 J) event, all of the samples except 16/8 dissipate moreenergy than the first pads. At higher energy, all of the samples except6/2 dissipate more energy than the first pads.

Dissipated energy has been identified as the critical element associatedwith preventing concussions, and 100 Joules has been noted in theliterature as a critical impact energy that results in concussions. Asummary comparison is thus made showing how much more or less energy isdissipated by the Bingham plastics than the first pads. In this case,the study looked for higher values, indicating more dissipation, thusless energy getting through to the wearer. The important results of thestudy showed that the Bingham Plastic materials far surpass the energyabsorption properties of the first pads from the Schutt helmet. In fact,the energy absorption of the Bingham Plastic is more than double in thecase of 12/2 and 16/8, and close to double for 16/2. This study providesa sound basis for the improvement disclosed herein, namely the use ofBingham Plastics as part of the structure of a removable insert in ahelmet that can provide improved protection against concussions than thestandard foam padding.

As noted above, an additional and optional feature of the inserts is theuse of fibers in the material. Two different sets of fibers wereevaluated as reinforcement to Bingham plastics—natural fibers (jute) andsynthetic fibers (PET). Fibers were cut to about 2-3 cm long andseparated. These fibers were mixed into a 4% PVA solution and 2% Boraxwas added to this mixture to create a fiber reinforced Bingham plastic.It is contemplated that fibers of a range of 0.1 cm-5 cm be used. Fiberslengths below and above this range are contemplated as well. Addition ofglass particles and hollow glass or plastic beads as reinforcementinstead of or in addition to fiber is also contemplated.

The Bingham Plastics with the use of the inserted fibers were tested forenergy absorption at 100 Joules impact and compared with the otherBingham plastics. The samples were 3 cm thick to be comparable with thefoam padding. The peak acceleration observed during impact of the fiberreinforced samples (“Nat Fiber” and “PET”) had relatively low peakaccelerations, with the natural fiber reinforced samples being lowerthan the orange foam padding, and lower than all the Bingham plasticsexcept 12/2 and 16/8.

The energy dissipated during a 100 Joule impact was also recorded forthe various 3 cm thick samples. The PET reinforced sample performedquite well, about the same energy dissipation and the 12/2 samples andslightly lower than the 16/8. The natural fiber reinforced samples hadthe highest energy dissipation of all the materials tested in thisproject. In this regard, an insert having a Bingham Plastic withinserted natural fibers appears to result in better performance for ahigh impact event.

Example Helmets

FIG. 1 illustrates a prior art helmet 100 including basic knowncomponents. An outer shell 108 is typically made of a hard plastic. Theshell 108 has an outer surface upon which is attached a facemask 102.The helmet 100 has an interior surface 110 to which is attached avariety of foam elements. Ear pads 104 are positioned near the wearer'sears. Other pads 106, 112, and 114 have various shapes and arepositioned in different regions in the interior of the helmet forprotecting the head from an impact. The deficiency of the standardhelmet is that the padding is not sufficient to prevent concussions.What is needed is an improvement in helmet technology that reduces thenumber of concussions which is easily implementable in existing helmets.The solution disclosed herein is, in one embodiment, a replaceableinsert that utilizes a different material than the standard foam andthat will dissipate more energy from an impact, thus reducing the energytransfer to the head of the wearer. The principles disclosed herein canalso apply to other helmets beyond football helmets, such as bikehelmets, motorcycle helmets, etc. In some cases, the helmets themselvesmight be disposable (and thus not use separate inserts) after one impactthat causes a change in the state of the Bingham plastic. The particularembodiment discussed next relates to a football helmet with removableand replaceable inserts.

FIG. 2 illustrates a variety of embodiments of inserts which can be usedto replace respective foam pads 106, 112, 104, 114 in a football helmet.Feature 202 represents an interior view of a crush system insert, which,in one embodiment, can be approximately ½ cm thick. Other thicknessesare contemplated as well. Feature 204 is a Bingham plastic, withcharacteristics disclosed herein. The plastic is placed in for example apolyethylene packet and attached to a plastic pyramid crush system 206as a support, which also includes fasteners to enable attachment to theinterior surface 110 of a helmet 108. Other materials of construction ofthe packet are contemplated as well, including mylar/polyester,polypropylene, cellulose, polylactic acid, or any other appropriatepackage material. Insert 202 is designed to replace earpiece 104. Thepyramid crush system 206, if viewed from the other side, would looksimilar to the crush system 210 shown in feature 208 of FIG. 2. Thegeneral structure of the Bingham plastic 204 can of course vary fromwhat is shown in feature 202. The shape, thickness and particularproperties of the Bingham plastic can also vary and be chosen based onany number of factors such as, but not limited to: head structure of theuser, weight of the user, position the user plays in a football game,helmet size relative to head size of the user (i.e., a larger helmet mayrequire a thicker insert 202), desirability of a level of protection,location of the head being protected, weight of the helmet, and soforth. For example, in once aspect, the thickness of crush system 206can be adjusted as well as the thickness of layer 204 such that theoverall thickness of insert 202 is 1 cm or 1 inch. In other words, thelevel of use of Bingham plastics in the layer 202 can be adjusted bymaking that layer thicker or thinner as desired with correspondingchanges to the thickness of layer 206. Such adjustments can be made foreach removable insert in the helmet 100.

Insert 208 shown in FIG. 2 includes a plastic pyramid crush system 210and a Bingham plastic layer placed in a packet 214. The packet can be ofany material. Another structure 212 is also a plastic structure that canbe used to attach the insert 208 onto the helmet shell 108. As anexample, insert 208 could replace foam padding 114 of the helmet 100. Inthis regard, feature 212 acts at least in part as a fastener to connector fasten insert 208 into the helmet. Another fastener 215 is alsoshown. Insert 208 can be used for example in the position on the helmetshown as feature 114 in FIG. 1. Feature 114 is the padding that isattached to protect the center of the forehead of the wearer. Astructure corresponding to feature 212 in FIG. 2 can be seen in the lefthelmet of FIG. 1, in the center and attaching a top bar of the facemask102 to the helmet 100. The various structures and thickness of layers210 and 214 of insert 208 can also be adjusted as with insert 202. Forexample, because this insert is positioned at a place on the helmetwhere significant impact occurs through tackling, the Bingham plasticlayer 214 can be thicker and the crush system 210 might be thinner inorder to provide improved protection.

FIG. 2 also shows another insert 216 with two different views, one fromthe top and one from the bottom. Insert 216 has fasteners 218 connectedto a pyramid crush system 220 which is then attached to a Binghamplastic layer 222 placed into a polyethylene packet. This insert snapsinto the helmet and can be used to replace foam inserts 112, 106 or 104.

The shape of the inserts is only meant to be exemplary as shall be seen.The overall thickness, the thickness of each individual layer of aninsert, the positioning and structure of fasteners, the structure of thecrush system layer, and so forth are all variable and differentvariations are contemplated. For example, the Bingham Plastic layer 204,214, 222 shown in FIG. 2 could be structured such that there are holesin various portions of the layer, or the layer could be smooth or rough,even or uneven across the surfaces.

In one aspect, the removable insert can include one or more holes orperforations that enable the Bingham Plastic, upon experiencing animpact meeting or exceeding a threshold level and that causes theplastic to convert to a liquid, enables the liquid exudes out the holeor perforation. FIG. 3 illustrates several different examples of a crosssectional view. Feature 300 shows an outer shell 302 of a helmet havingan inner surface 304 to which a fastener 306 connects the shell 300 toan insert 309 including a first layer 308 and a second layer 310. Onelayer is generally considered to be of a standard foam type layer andthe other of layer 308, 310 is made from a Bingham Plastic. The layers308, 310 are interchangeable. Fastener 306 can be any type of fastener.It is preferable that fastener 306 represent a fastener that enables theinsert to be removable.

FIG. 3 further shows feature 312 with a different fastener 316connecting the insert 314 to the inner surface 304. The insert 314 inthis case is all made from Bingham plastic. In one embodiment, feature316 represents a plastisol or other low to moderate rubber material thatis positioned on the inner surface of the helmet 302. The plastisollayer 316 could double as a fastener to the removable insert. In thisregard, the discussion herein about the plastisol layer adhered to theouter surface could also be applicable to the inner surface. The innersurface plastisol layer may or may not be used as an adhesive for aremovable insert. The plastisol layer may be configured such that thereis no other removable insert but the plastisol layer is positioned totouch the head of the user.

FIG. 4 illustrates a variation in which an electronic system is used toprovide a signal indicating that the Bingham Plastic has changedconformation due to the change in state such that it is no longereffective. This would be applicable if an irreversible material wasused. In feature 400, the layer 310 includes a detector and transmitter402 which transmits a signal to a remote device 404 having an antenna406 such that a person such as a coach or a parent can be notified ofthe potential for a concussion or other injury. Thus, whether it isthrough a gyroscope or a system of accelerometers that detects a largeenough impact at or above a threshold value, or whether the detector 402identifies when the Bingham Plastic has converted from a solid to aliquid, the detector/transmitter 402 would transmit a notificationsignal of that event. In that case, the user would remove the insert 309and replace it with another insert before using the helmet again.

FIG. 5 illustrates another aspect of this disclosure in which the helmet400 has attached to the inner surface 304 of the shell 302 an insert 309with two layers 308,310. Embedded within one of the layers is acomponent 502 that can be mechanical or electrical. In an electricalembodiment, the component 502 detects whether the Bingham Plastic inlayer 310 has changed state from a solid to a liquid to absorb animpact. If so, the component 502 communicates with another component 504in the surface of the shell 302. Where these components are electrical,they could communicate via a wireless means such as BlueTooth or someother protocol. The component 504 provides a signal to the user that canbe seen to indicate that the insert should be replaced. For example, ared LED light could turn on or a sound could be made to indicate andwarn that the insert 309 should be replaced. There are other mechanismsas well disclosed below that provide for various means of warning.

In one type of device, the phase change is monitored by a change incapacitance. In another type of device, a change in phase causes adisplacement of wires or other sensors that trigger the device.

FIG. 6 illustrates various shapes of inserts, some with holes andopening in them. Insert 602 is “L” shaped. Insert 604 is round. Insert606 is rectangular and has optional holes 607 which can provide someflexibility and expansion space when the Bingham Plastic changes phase.Insert 608 is “I” shaped with an optional opening 609 also to allow forexpansion. These configurations are provided as examples only. Any shapewith or without openings or holes within the shape are contemplated. Theopenings may be provided as a way to reduce the weight of the insert, asthe inserts with Bingham Plastics generally weigh more than the standardfoam.

The shape of the inserts or other structures associated with the helmetcan be made via patterns such as, for example, patterns of triangles,squares, regular or irregular rectangles, patterns of pentagons andhexagons or other polygons. The structures can also have cutout sectionsbetween or internal to shapes.

FIG. 7 illustrates a number of variations on this disclosure withrespect to a cross sectional view of an exemplary insert. Insert 700includes fasteners 704, 706 and a first layer 708 with a second layer710. A top portion 702 is generally nearest to the inner surface of theouter shell of a helmet. The right side of the layers is angled. Thisembodiment shows how the shape on one or more vertical surfaces can beangled. Insert 712 shows layer 714 and layer 716 such that the interfacebetween these two layers is angled. Such an approach could be used wherea thicker Bingham Plastic layer (for example, layer 716) might bedesirable at a particular location within the helmet. In such a case,over the distance of the insert 712, there may be another portion thatdoes not need as much Bingham Plastic in another portion of the insert712 due to the configuration of the head of the wearer or likelihood ofa concussion due to impact at that location.

Insert 718 shows layer 720 and 722 with a curved interface between thelayers and layer 722 having a curved lower surface. Insert 724 shows alayer 726 with an internal layer 728. In this case, the Bingham Plasticcould be the layer 726 or the layer 728, or they both could have BinghamPlastic but with different characteristics. Layer 728 could be open aswell to allow for expansion or flow of liquid in the transition. Layer726 could be more traditional foam while layer 728 could be the BinghamPlastic. Insert 730 illustrates a height “d” for layer 732 which asnoted above can generally represent the height of any insert disclosedherein and is variable. It is noted that any of the configurationsdisclosed herein can be interchangeable in a part or completely. Forexample, insert 712 could be combined with 718 such that the lowersurface of layer 716 is curved in the same way that the lower surface oflayer 722 is curved.

FIG. 8 illustrates another embodiment in which layer 804 is shown asanother layer between the shell 302 and the fasteners 306. Insert 800can include layer 802 which could be a Bingham Plastic layer or a layerof foam padding or other type of cushioning material included forcomfort.

The above embodiments focus on the use of Bingham Plastics as part ofthe structure of a removable insert on the inner surface of the helmet.The next aspect of the helmet embodiment is the disclosure of the use ofplastisols on the outer or inner surface of the helmet. These twoaspects of course can be separate or combined into a single helmet. Abrief discussion on the studies performed using various plastisols ispresented followed by a description of the helmet having one or moreplastisol sections, portions, or layers attached to the outer surface ofthe helmet.

Discussion of Plastisol Study

Next is discussed the preparation of the helmet prototype disclosedherein with respect to a plastisol layer on the outer surface of ahelmet. The process of preparing the prototype helmet using an outerlayer of a plastisol is first presented. A plastisol is a suspension ofPVC (vinyl chloride) particles in a liquid plasiticizer. When heated toan appropriate degree, the plastic and plasticizer mutually dissolve anda permanently plasticized solid is the result. To create the solidhelmet prototype, the existing helmet was stripped of all its hardware;face mask, buttons, etc. Sheets of two different hardness plastisols(Shore Hardness 16—henceforth SH16, and Shore Hardness 90—henceforthSH90) were baked. The instructions on how to bake these and all otherplastisols are specified herein. The softer layer, SH16, was adhered tothe helmet first. Following this, the harder, SH90, was applied on topof the softer SH16. To apply the softer layer, the sheets were cut intostrips approximately three to four inches wide. Each strip was laid onthe helmet to mock up the location for it to be applied, then PVC primerand solvent cement were applied to the back of the strip as well as thehelmet. Alternatively, a single layer of plastisol could have beenapplied over the entire helmet using molding techniques.

The strip was then held in place while the solvent set, around fiveminutes. After the solvent was set another strip was placed next to itand trimmed to adjust for the curvature of the helmet and the strip itwould touching. The primer and solvent were then applied, as before,also repeating the step of taping the strip in place. This was repeateduntil the entire exterior of the helmet was covered in the softer SH16plastisol. Then the SH90 plastisol was adhered on top of this. To applythe black the sheets were cut into strips, again as needed, but of awidth of approximately one to one and a half inches. The smaller stripsallowed for greater flexibility on the much stiffer material. The samesteps for applying the strips were taken, but with a longer time allowedfor the solvent to set, approximately ten minutes. Again, this wasrepeated until the helmet was covered in SH90 plastisol. Cracks betweenlayers were then filled by applying SH90 plastisol in its liquid stateto the cracks, a small section at a time to prevent running. The liquidwas then cured in place using a heat gun. FIG. 9 illustrates theembodiment. The entire helmet was then sanded and painted. Finally allthe hardware was reinstalled. Alternatively, the harder layer could beformed as a single layer using molding techniques and could be adhereddirectly to the softer layer while in a liquid state.

A segmented helmet prototype began the same way that the solid helmetdid, by removing all the standard hardware from the helmet. Five sheetsof layered Shore Hardness 4 (SH4), and Shore Hardness 16 (SH16)plastisols were baked. The SH4 was baked first and then the SH16 bakedon top of it. The layered sheets were then cut into shapes from apredetermined pattern. The pattern has two of every part simply mirroredfrom each other, except the middle three patches. Alternatively therecan be non-symmetric patterns. FIG. 10 illustrates the different partson the outer surface of the helmet. Each patch was then glued in placeusing super glue, and then the patches were held in place to allow theglue to set. Alternatively, the patches could be formed directly ontothe helmet using molding techniques. The final step was to refit all thestandard hardware and internal pads to the helmet. Similar techniquescan be used to adhere the plastisol layer to the inner surface of thehelmet.

The method used to develop the plastisol embodiment is described next.The plastisols used were described by their Shore Hardness values. Thedifferent plastisols used were pigmented for simple distinction: No. 4(yellow), No. 16 (blue), No. 33 (red), No. 65 (green), and No. 97(black). Of course any pigmentation choice will do. An oven was used tobake the samples. The plastisols were baked at a temperature of 350 F ina baking pan. The oven is level to avoid uneven thickness with the bakedsheets. 100 ml gives 1 mm thickness when using a 6×9 steel pan. A thinsheet of 1 mm of No. 4 plastisol (100 ml volume) (yellow), was baked inthe oven for 8 minutes at 350 F.

After 8 minutes, the pan was placed on a level surface and allowed toset for 5 to 10 minutes. (Note: the yellow plastisol was still fluidwhen taken out of the oven. If not placed on a level surface, uneventhickness resulted in the sheet).

The time required for making the sheet is dependent on the volume used.The use of ratio and proportions can be used to determine how much timeit should be baked. For the No. 16 plastisol (blue), for a sample of 1mm thickness, the baking time was 6 minutes at 350 F. Samples wereremoved from the oven and let cool for 5 minutes. The No. 16 plastisolsets in the oven. However, it is advisable to place all samples on alevel surface. For a 2 mm thickness, the baking time was 9 minutes withcooling for about 5 minutes. As the thickness of samples increases, thebaking time is increased by 3 minutes.

For the 1 mm thick, No. 33 plastisol (red), the bake time at 350 F was10 minutes and was allowed to set on a level surface for 5-10 Minutes.The ratio and proportion can be used to determine the how much time isneeded to bake thicker sheets of No. 33 plastisol.

For the 1 mm thick No. 65 plastisol (green), the bake time at 350 F was8 minutes. No. 65 sets in the oven, however, the sheets were placed on aflat surface to cool. Ratio and proportion can be used for thickersheets of No. 65 plastisol.

For the 1 mm thick No. 90 plastisol (black) sample, baking took place at350 F for 10 minutes. This plastisol also sets in the oven. The ratioand proportion can be used to determine the how much time is needed tobake thicker sheets of No. 90 plastisol.

A layer of a given material is baked according to the above procedures.Before letting the layer completely cool, but after ensuring theplastisol was no longer liquid (in the case of No. 4), the next layer ofmaterial was poured on top of the existing layer to yield a multi-layerplastisol. The multi-layer plastisol was then replaced in the oven forthe time and temperature indicated for the given material. This processwas repeated if necessary for multiple layer systems.

In an open mold it was important, but not necessary, to maintain a levelpan to keep uniform thickness. In a closed mold configuration such aswould be employed in a production environment, this would not be asimportant. There are other rubber materials that can be used besidesplastisol, including styrene-butatdiene-styrene andstyrene-isobutylene-styrene, and urethanes.

Plastisols with “Shore A” hardness values of 4, 16, 33, 65, and 97 werestudied. Shore A hardness refers to a material's resistance toindentation. The “A” scale is for softer plastics. Samples were producedusing these materials in single, 3, and 5 layer configurations.Additional samples were produced in 2 layer and “feathered”configurations. Shear testing, compression testing and impact testingusing the various configurations of plastisols were performed. Impacttesting on a helmet having at least one plastisol layer on its outsidesurface was performed by releasing a 5.5 kg sphere with approximately100 Joules of potential energy towards a strike plate holding the sampleunder investigation. The potential energy of the strike plate afterimpact was measured and the difference between the two was a measure ofthe absorbed energy by the material receiving the strike. The test wasperformed initially with an approximately 3 kg strike plate and thenagain with an 8 kg strike plate.

The impactor, a shot put suspended by cable, was released from a fixedpoint to impact the strike plate at its lowest point. The strike platethen moves away in the direction of strike and the movement of the platewas recorded using video. The video was analyzed frame by frame todetermine the highest point of motion of the strike plate and theinitial kinetic energy as well as the final potential energy wascalculated.

Three replications were performed for each impact condition, both forlight and heavy strike plates. The light strike plate had a mass of 3.1kg and the heavy strike plate had a mass of 8.3 kg. Of interest is theenergy absorbed by the target. The absorbed energy was calculated bycomparing the energy transferred to the target without any plastisols onit to the energy transferred when the plastisols are in place. Thedifference between the two represents the absorption of energy from theplastisols.

Different configurations of plastisols were considered for evaluation.In a baseline set, samples made of a single layer of each hardness ofplastisol were produced. Data was gathered to determine the effect ofhardness for single and double layer samples on the absorbed energy ofthe target. A 100 Joule pendulum impact was tested. Two frames wereused—a light 3.1 kg frame and a heavy 8.3 kg frame. Double layer sampleshad a thin (1 mm) layer of SH97 plastisol on the strike surface and athicker layer of software material on the obverse side. For a smallShore A hardness, with the light weight target, the soft material (SH4)absorbs the most energy, but then there is vanishing effect. When theheavy target was used, there was virtually no effect of the materialwhen in a single layer. From a dynamics perspective, the heavier targetresulted in less energy absorption because the increased mass means thatthe potential energy associated with deforming the target can betransferred back into kinetic energy. The double layer material, havinga rigid surface that meets the impactor, shows more energy absorbingproperties when struck.

The mechanism of energy absorption is primarily plastic deformation ofthe material. The material goes through dramatic plastic deformation asa result of impact. The 4 hardness material had complete rupture anddelamination from the hard strike surface. The 16 hardness materialshows yielding failure and partial delamination from the hard strikesurface.

The same data was calculated in terms of the additional energy absorbedby the material—taking the energy absorbed divided by the energytransferred to the strike plate when no material was present. 3 and 5layers configurations were also tested.

A second test configuration was also studied. The configuration waschanged to an oblique impact, where the strike plate was rotated 60° offvertical to allow a shearing type of oblique blow. The position of thestrike plate before and after impact under this oblique impactconfiguration (at maximum displacement) were determined and the methodof analyzing the energy absorbed by impact proceeded as before. Thepurpose of this test is to evaluate glancing impact on the material.Glancing impacts have a tangential displacement component which canapply enhanced shearing energy. The energy transferred through aglancing blow is a combination of factors, including the compressivestiffness of the material and the shear stiffness.

Different material configurations were tested as before and the resultsare presented here. Only the heavy frame was used for this testing. Forsingle layer materials, the energy absorbed during impact follows acomplex path, with a surprising high value for the SH97 material. It ispossible that the SH97 material provides a slippery surface for theimpact to slide off instead of transferring energy to the target. Thethree layer materials subject to oblique impact showed behavior that isexactly opposite of what was expected. The absorbed energy increasedwith core material hardness, instead of decreasing. The five layersystems were relatively insensitive to the softness of the second andfourth layers.

Low energy impact was studied as well. The study discussed above used100 Joules as the impact energy. An additional round of testing wasperformed using 33 Joules as the impact energy. The value of 100 Joulesrepresents the upper level of impact from the literature. 33 Joules isestimated to be a more common level of impact. Depending on size of thearea it is spread over, up to 75 Joules can potentially be a deadlyimpact. Tests were performed in the vertical, compression impactconfiguration to evaluate the behavior of the materials under lowerenergy of impact.

The study included charting the absorbed energy from 33 Joule impact onsingle layer and 97/x configurations (where a thin, 1 mm, layer of 97 isapplied to the strike surface). There is an additional sample, labeled“Feathered” and marked as a diamond, where the material was made asSH97/65/33/16/4 to gently transition from the SH97 value to a value of4. In the data, the feathered sample absorbed between 1.3 and 3 J ofenergy. The data was indicated as a Shore A hardness value of 38 for thefeathered sample—an average of the hardness of the feathered layers.

All of the various 3 and 5 layer combinations were also tested at 33Joules impact. The highest impact absorption in the study was thefeathered sample which absorbed between 23 and 30 percent of thepotential energy transferred. There appeared to be a strong trend at 33Joules impact—particularly the softest materials dominate the energyabsorption. Even layered systems tend to fall on the trend of thebehavior of the softest layer of the system. The 5 layers samples allabsorbed about the same percentage at about 15% no matter what the levelof the Shore A Hardness level. The 1 layer sample absorbed more energyat the software Share A Hardness values below 30.

Helmets with a Plastisol Outer Layer

In another embodiment, protection on the exterior of the helmet wasapplied using plastisols prepared as described above. Plastisolmaterials were applied to the exterior of a helmet to demonstrate thepotential for shear absorbing performance. Weight is a significantconcern in this situation, so a thin (3 mm) system or layer was appliedto the exterior consisting of a layer of SH33 at the outer surface ofthe helmet and a layer of SH97 at the exterior. It was determined thatit was not necessary to have a SH97 layer at the interior as the helmetitself provides the stiffness.

Flat sheets of material were made and then transferred to the exteriorsurface of the helmet as shown in FIG. 9. The curvature of the helmetintroduced difficulties due to the differential strain from interior toexterior. Because the exterior (in tension) is the hardest material,curving the pieces resulted in primarily compression of the softerinterior material, which leads to internal normal strains and interlaminar shear trying to separate the layers. The helmet formed with33/97 Hardness is illustrated in FIG. 9 after the hardening. The pinstriping 908 was added to disguise the seams that formed between stripsof materials.

FIG. 9 illustrates three helmets 900 with a thin layer of plastisolattached to the outer surface of the shell. Helmet 902 shows layers 910which represent a thin layer of plastisol attached to the outer surface.The layer can be between 0.5 mm and 5 cm in thickness and attached byany known adhesive to the shell. Feature 908 represents spaces, stripsor gaps of space in which there is no layer. The gaps 908 provide someexpansion space for the plastisol 910 layers in case of impact. Helmet904 shows a frontal view of the layers 910 and the gaps 908. Helmet 906shows another side view.

FIG. 10 illustrates another set of helmets 1000 in which helmet 1002 hasspaces 1008 and plastisol layers 1010. As is shown in helmets 1002, 1004and 1006, the plastisol layers 1010 can have different shapes and sizes.These layers can be of varying thicknesses, sizes and shapes dependingon the location on the helmet and need for protection at a particularlocation. Gaps 1008 are also shown in between the plastisol portions1002, 1004, 1006.

The strips of plastisol were adhered to the helmet using PVA adhesive(typically used for joining PVA plumbing). The material was spraypainted afterwards to smooth out the appearance because of the stripformation method. The helmet with the exterior layers was heavier thanthe original due to the high density of solids in the plastisols and theapplied paint.

An additional prototype exterior helmet was made to demonstrate theconcept more fully. Although the material choice (4/16) is not anoptimal choice for true impact performance, 4/16 is a good choice todemonstrate the concept. The 4/16 material easily shears under handpressure so can be used to explain the process. The material was appliedto the exterior of the helmet with gaps 908/1008 between the pads tofurther demonstrate the shearing capability and to reduce the totalamount of increased weight in the helmet. Having free edges allows formore motion. The plastisols were cut into shapes and adhered to thehelmet using glue or superglue (cyanoacrylate).

In production, mixing of plastisols or other rubbery elastic plasticswould be achieved in an extruder or other industrial blending equipment.The helmet coating will be produced with closed molds or using spin orrotational molds. Full scale production equipment is used to generatethe helmet plastisol coatings.

Cartridge Embodiment

Next, this disclosure continues with FIG. 11 and another embodiment ofthe insert or cartridge which is replaceable. FIG. 11 illustrates anexample embodiment of the present disclosure. A cartridge or insert 1116is shown as insertable into a helmet 1110. It is noted that the helmet1110 could also represent any surface or any protective layer such as ashield, body armor, wall or any other protective layer in which acartridge 1116 as is disclosed herein could be inserted. Cartridge 1116is a replaceable insert or cartridge that can be part of the outer shell1110 of the helmet. In general, it is noted that the concept covered inthe present disclosure is a removable cartridge which can be positionedwithin the helmet 1110 at a high impact location. In this case, a highlyeffective energy dissipation structure can be employed within thecartridge 1116 which, may be irreversible. For example, if the use ofBingham plastic as applied to the cartridge 116, then upon asufficiently high impact, the energy is dissipated by the conversion ofthe Bingham plastic from a rigid body to a viscous or Newtonian fluid.The displacement occurring when the fluid flows may be inconvenient toreform, that is irreversible. Therefore, the present disclosure providesfor replacing the cartridge in the helmet with a new cartridge withBingham plastic which is in the appropriate place in the cartridge andis a solid.

As is shown in FIG. 11, the example structure includes the cartridge1116 with various features. The Bingham plastic 1118 is represented asbeing within the cartridge. The positioning is merely exemplary as theBingham plastic will be positioned throughout the cartridge in such away as to be able to absorb the energy of an impact on the cartridge1116.

When an impact causes the Bingham plastic 1108 to convert to a liquid,the liquid will likely flow into one of several reservoirs. For example,an opening 1114 is shown at an edge of the Bingham plastic 1108 whichleads to a channel 120 having an opening 1122. This opening 1122, whenthe cartridge 1118 is positioned in a receiving parameter 112 tocoincide with an opening 1132 which connects to a reservoir 1134. Inthis example, the reservoir is found within the helmet 110. In thiscase, this allows the Bingham plastic in its fluid state to flow awayfrom the cartridge 1116 and into a separate reservoir. Similarly, asecond opening 1146 is shown in the cartridge 1116 which includes achannel 1124 which leads to an opening 1126. This opening corresponds toopening 1136 in the helmet 1110 which leads to a second reservoir 1138.It is contemplated that these reservoirs may be interchangeable withinthe helmet. In other words, if an impact is received on the cartridge1116 and the Bingham plastic 1118 converts from a solid to a liquid andthe first reservoir 1134 and the second reservoir 1138 (or simply one ofthe reservoirs) is filled with fluid from the Bingham plastic, thenwhile the cartridge 1116 may be removable and replaced, the reservoirs1134 and/or 1138 may also be removed and replaced with an emptyreservoir.

In another aspect, the channel 1120 could lead to a reservoir 1130within the cartridge 1116. A second reservoir 1128 is also shown asbeing connected to the reservoir 1124. Thus, in an ultimate embodiment,the reservoir which receives the viscous or Newtonian fluid can bepositioned within the cartridge 1116 such that the cartridge iscompletely integrated. Feature 1142 of cartridge 1116 generallyrepresents a fastening mechanism which corresponds to feature 1140within the helmet. There may be a number of different structures whichcan be used to replaceably secure the cartridge 1116 within the helmetand any and all such techniques and structures are contemplated aswithin the system 1100 disclosed in FIG. 11.

The helmet can include a helmet structure having an opening with aperimeter. The perimeter defines the opening which will receive thecartridge. The cartridge includes a complimentary structure to theopening and includes a structure which, when absorbing energy from animpact upon the cartridge, converts the structure in form to absorb theenergy in an irreversible manner such as by converting from a solid to aliquid. A fastening mechanism removeably fastens the cartridge in theopening of the helmet. The cartridge includes a top layer positioned toreceive an impact and an absorbing layer which includes a material whichabsorbs energy from an impact in an irreversible manner such as byconverting from a solid to a liquid. The fastener removeably fastens thecartridge into an opening in a larger structure.

FIG. 12 illustrates another example embodiment 1200 of the cartridge1116 in which one or more reservoirs are positioned within thecartridge. The Bingham plastic 1118 is shown with a particular structurewithin the cartridge 1116. An opening 1144 leads to a first reservoir1134 and an opening 1146 leads to a second reservoir 1138. These canrepresent one or more reservoirs into which the Bingham plastic wouldflow upon a hit of sufficient impact. The hit on a helmet and thus thehit on the area of on a cartridge 1146 can occur in several locationsand the positioning of the Bingham plastic 1118 throughout this area aswell as the positioning of reservoirs 1128 and 1134 can be made based ona statistical probability of a position of hits within the area of thecartridge 1116. Therefore, the particular locations within the cartridge1116 in FIG. 12 are merely illustrated.

In some cases, the cartridge may receive impacts and cushion thoseimpacts but the force may not be sufficient to cause the Bingham plasticto convert from a solid to a liquid. Therefore, a football player maynot recognize when the cartridge needs to be replaced or not. In oneaspect, a notification symbol 1148 can be in communication 1150mechanically or electrically with a reservoir 1128 and/or the reservoir1134. There may be several different mechanisms which either canillustrate via a display or a color representation on the helmet thatthe Bingham plastic has sufficiently converted from solid to liquid soas to reduce its effectiveness. For example, the Bingham Plastics mayinclude two different layers in which each layer has a different color.When an impact occurs that causes the solid to change to a liquid, thetwo layers may mix revealing a color that indicates to a user that thecartridge needs to be replaced. The concept of having different coloredlayers is discussed more fully below with respect to FIG. 13. Electricalsignals which can be visual or an audible signal such as a chirping canbe employed to notify the user of the need of replacement.

In one example, the feature 1148 can represent an electroniccommunication 1150 with the reservoir wherein a sensor indicates thatthe reservoir has filled with the viscous fluid of the Bingham plasticand a signal can be sent wirelessly and electronically to a receiverwhich would then provide notification to a person such as a coach or atrainer that a particular players cartridge has been triggered and thusthere is a need for a replacement cartridge to be placed within thehelmet. Other sensors and notification systems can be provided such as asound or an impulse or a light and so forth. Sensors could be providedin one or more channels 1120, 1124 or any place along the path that theviscous fluid would flow in order to provide the appropriatenotification that the helmet is no longer safe but has absorbed animpact and has successfully prevented potentially a concussion.

A benefit of the present approach is that rather than having entirelyreplaceable helmets, the system could provide the optimal amount ofprotection at a particular high impact location upon a helmet. Thus, thepresent approach would not require the entire replacement of helmets butonly the replacement of a portion of the helmet which can utilize afeature such as a Bingham plastic or any of the other features disclosedin the priority applications.

In other words, another embodiment could be utilizing a foam structurewith a varied density and having a particular shape. In one aspect, whena hit occurs at a particular level of force, the foam structure maycollapse or may absorb the energy of the impact in such a way as to benonreversible. Accordingly, the concept of a replaceable cartridgeexpands beyond the use of Bingham Plastics but involves any applicationof an absorbing structure within the cartridge that absorbs the energyin an irreversible way.

FIG. 13 illustrates another embodiment that relates to how to providenotification of when a Bingham Plastic has changed phase due to animpact to the insert and thus the insert needs to be replaced. Thisconcept was introduced briefly above. The insert 1300 in FIG. 13includes two layers 1302 and 1304. These two layers can both be madefrom the same or different types of Bingham Plastic. However, thedifference in FIG. 13 is that there is a certain color scheme to eachlayer such that when an impact occurs, and the solid turns to a liquid,it causes the layers to blend physical which can reveal a color to theuser.

For example, layer 1302 could be made of a red Bingham Plastic and layer1304 could be white. If the inset 1300 is placed in a helmet, then theuser would see the layer 1304 white layer. However, if an impact causedthe insert 1300 to absorb the energy to the level where the plasticschanged phase, then the red in layer 1302 would blend with or bleed intothe layer 1304. The user could check the color and see that the layer1304 was no longer white but had some red showing. This would indicatethat the insert needed to be replaced. It is noted too that while theheight of layer 1302 and 1304 appears to be equal in FIG. 13, that thisis only an example figure. The two layers may be of a different height.For example, layer 1302 may be much thicker than layer 1304 so as tomore easily show when the plastics have turned to liquid. The relativethickness or shear thresholds of each layer can be tailored to the levelof impact which will indicate a change need to be made in the insert.

FIG. 14A illustrates the insert in more detail in a helmet 1400. Theouter shell 302 is attached to the insert via a fastener 306. Optionallayers 804 and 308 can be constructed either of a foam structure, aBingham Plastic structure or some other structure. The Bingham Plasticlayer 310 can include a first layer 1404 of one color, such as red, andanother layer 1406 of another color, such as white. As noted above, whenan impact occurs, the color in 1404 will bleed into or blend with thecolor in layer 1406 such that it provide “notice” to the user that theinsert should be replaced. There also could be an electronic noticeprovided in which a signal is sent to a module or device 1402 in thehelmet 1400 that turns a light on or provides some other indicator thatcan be seen from the outside of the helmet.

FIG. 14B illustrates a first insert 1410 and a second insert 1412 anddemonstrates what the “notice” could look like. Here, the impact areawas between insert 1410 and 1412. While most of the viewed surface areaof these two inserts is white, there is a portion that has coloration inportions 1414, 1416. If the user had an excessive impact in a game or inan event like a bike accident, they could take their helmet off and lookat the inserts. If the inserts show what is illustrated in FIG. 14B,then the inserts would be replaced.

While two layers are shown, it is contemplated that the insert couldhave more than two layers of different colored Bingham Plastics in theinsert. For example, the insert could have 3, 4, 5, 6 or 7 or morelayers.

A method embodiment is shown in FIG. 15 and illustrates a processassociated with the use of the inserts. An exemplary method includesreceiving an impact on a helmet (1502), absorbing at least a portion ofthe impact in a nonreversible (or reversible) structure (i.e., theinsert) (1504). The impact is absorbed at least in part by the BinghamPlastic in the insert of the helmet converting from a solid to a liquid.The method further includes providing an indication of the change from aslide to a liquid based on the impact (1506). The indication could be achange in color, a change indicated by electronic mechanisms, a changein shape or texture of the insert, or in any other fashion. Finally, themethod includes replacing the structure with a fresh structure (1508).The insert structure could also be reversible in some manner. Not eachstep above is necessary to practice the method as any one or more stepscould be excluded.

This method covers the basic aspect of use of the cartridge disclosedherein. It includes the concept of the cartridge within a structure 310absorbing an impact to such a degree that the structure within thecartridge changes its form in an irreversible way. In this case, thecartridge is no longer useable to absorb impacts and it needs to beexchanged. Therefore, the method includes the feature of exchanging theenergy absorbing structure that has changed its form in an irreversibleway with a new cartridge which has its structure intact inasmuch as ithas not yet been changed via the absorption of the energy of an impacton the cartridge.

FIG. 16 illustrates different zones 1600 within a helmet. Zones 1 and 2are at the rear portion of the helmet; zones 3 and 4 cover the sides ofthe head and ears; zone 5 is in the front of the head or the foreheadand zone 6 covers the top of the head. These different zones arepresented to show that different structures having Bingham Plasticscould be used for different zones. The use of the Bingham Plastics canprovide a heightened protection; the most strategic zones may haveinserts with additional Bingham Plastic by way of a thicker layer of theplastic. For example, the inserts in zone 5 might have ⅔ of thethickness be a Bingham Plastic layer while the remainder is standardfoam. The inserts in zones 1 and 2 may have a layer of Bingham Plasticthat is ¼ of the entire thickness of the insert or have no Binghamplastic at all. Other zones may have lighter inserts as well to balanceout the overall weight or responses to different types or levels ofanticipated impact.

FIG. 17 illustrates the transmission of load 1700 in compression orimpact. The material shown can be, for example, a Bingham Plastic,plastisol or other material. There are multiple scales of reinforcement1702, 1704 that mediate load transfer between the reinforcementparticles. The load of impact is more efficiently transferred from thepolymeric matrix, e.g. the Bingham plastics, to the smaller particles.These particles transfer load to the larger reinforcements. Thesereinforcements may be particles, fibers or flakes of variouscompositions.

FIG. 18 illustrates an example graded foam structure 1800 that can beutilized in any layer of a helmet overall or in any layer of an insertas disclosed herein. As the foam cones 1802 throughout the activedissipation layer take up load, they absorb impact by expanding into theintegrated expansion zones 1804. The graded foam structure layer can be,for example, layer 308 in FIG. 14A. As can be seen as well, the densityand structure of the foam is graded from a top portion or a base portion(the widest part of the pyramid structure) to the pointed end of thepyramid structure. It is noted that the foam structure disclosed in FIG.18, as well as any other structure incorporated herein by referenceabove, can be applied as a layer in the insert or cartridge disclosedherein. Different types of structures disclosed or incorporated hereincan also be mixed or blended to create a layer as well. For example, atop portion of a graded foam layer can be triangular and a bottomportion can be of a different shape, such as semi-spherical orrectangular.

In this embodiment, the graded foam structure expands laterally ratherthan compressing under applied load. Upon the force being applied, thefoam displaces laterally to absorb energy without displacement of theinner surface of the insert relative to the surface of the head assignificantly or at all. This reduces the amount of energy transferredto the head of the individual, thus reducing the probability of injury.The structure of the graded foam can be triangular, circular,rectangular, or any other structure. The graded foam can be positionedon two structures in a mirrored relationship or two structures with adifferent shape. The important feature of the structure is that there bespace into which the foam can displace laterally to absorb the energy.

The graded foam can be a graded combination of polyurethane foams withdifferent mechanical modulus to provide a target range of deformationthreshold energies. In other embodiments, the target range can beachieved using polyurethanes of different chemical or physicaldensities. The target range can be achieved using polyurethanes withdifferent physical or chemical densities or modulus combined withnanoparticulates and/or microparticulates of silica. For example, theparticulates can be other ceramic, metal or plastics. In otherembodiments, the plastic can be other flexible foam material, e.g.foamed styrene butadiene rubbers, styrene-butadiene-styrene rubber, orco-polyesters, co-polyamides, or co-polyacrylates.

In another embodiment, the material can be a plastic or a rubber with alow modulus that displaces laterally at a shear threshold. Upon theforce being applied, the material displaces laterally, which will slowthe transfer of shear energy rather than allowing shearing energy to betransferred rapidly to the surface below. Such a structure reduces thepeak energy transferred to the head of the individual, thus reducing theprobability of injury.

Additional Impact Structures

Another embodiment of this disclosure relates to other impact handlingstructures beyond helmets. FIG. 19 illustrates a blast and several wallswith structures to handle the blast 1900. A blast usually has twocomponents: a rapidly expanding pressure 1902, or shock, wave thatknocks over barriers and objects, and projectiles with sharp, jaggededges 1904 that impact with often devastating effect. This embodimentcovers a proposed fabric can be rapidly deployed: against the back face1910 of an existing wall 1906, in which case the wall may be damagedduring the blast but is reinforced to withstand the blast for laterrepair and mitigate secondary damage to objects or persons outside thebuilding; or free mounted to existing or temporary poles 1908, in whichcase the impact surface allows the pressure front to pass throughwithout impediment but stops projectile debris, while the back surfaceexpands while dissipating the energy of the compression front. Thefabric may not provide full protection against multiple blasts. It isanticipated that these fabrics can be reinforced with variousconfigurations of the components previously explicated. For example,plates covered with Bingham Plastics or multiple rubber layers such asplastisols, can be used to provide surfaces within the fabrics to absorband dissipate impacts from large shrapnel components. Such materialscould also be employed in other protective ways such as on panelsattached to vehicles or inside doors or vehicle surfaces and evenwindows.

FIG. 20 illustrates a 3-D grid model of the proposed fabric beingassembled into a box-like configuration to contain, for example, a trucksuspected of containing explosives. Depicted in FIG. 20 are severalstages of setting up a first wall 0102, a second wall 2004 and theentire constructed system 2006. Feature 2008 illustrates the response ofthe outer layer (described below) that expands moderately as itdissipates the energy of the shock wave from the blast. The blastsurface in FIG. 20 is made from, for example, one or more of the variousdisclosed materials.

FIG. 21 illustrates potential layers in the fabric portable wall.Feature 2102 is a blast surface layer which is a shrapnel-catching layerwith high tenacity but is porous. The material 2102 could be woven ormultiaxial warp knit, for example. Fabric 2104 is a gas containmentlayer which allows internal fiber dis-bonding for energy absorption.Layer 2104 can be nonwoven or weft knit or some other extensiblematerial for example and embedded in an elastomeric system. Layer 2106is an additional mass and shrapnel containment layer in the center ofthe system. This layer may have ceramic tiles to absorb energy throughcatastrophic failure. The layer 2106 is permeable to gas. Thus, any ofthe walls or ceiling depicted in FIG. 20 can be made from one or more ofthe layers described in FIG. 21. Any combination of layers iscontemplated as well. For example, wall 2002 could include a blastsurface layer 2102 with a gas containment layer 2104. The layer 2102 and2104 could be adjacent to each other and essentially connected togetheras one combined material, or may be set up as separate layers that areseparately attached to a floor and/or ceiling. Depending on thepotential explosive device, different levels of protection can bequickly constructed to have a system like that shown in feature 2108that will absorb the impact. The layers can be mixed and matched.

The tiles shown in FIG. 21 can be ceramic or other materials, such as aplastisol or a Bingham Plastic. They could alternatively be plates ofthe explicated materials. The plates can be of uniform size, e.g. about2 inches square to simplify folding the fabric. The plates may be ofdiffering sizes, perhaps mathematically designed, to optimize thereaction to shrapnel of different sizes. The plates may be overlappingin order to provide maximal coverage, or to continue to provide completecoverage even as the fabric layers expand to dissipate the blast front.

A surface used for blast protection can be made from a cotton fabriclayer that is structured such that a yarn will break on the applicationof a shear threshold. Upon the force being applied, the yarn tears andruptures so as to consume energy in breaking. This reduces the peakenergy transferred to the surface of the structure or individual, thusreducing the probability of damage or injury. In another embodiment, theyarn can be made from an appropriate chemistry and diameter to have atarget failure threshold, e.g. polyester, nylon, or glass.

In another embodiment, the fabric layer can be a helical-auxetic yarnthat becomes thicker as it extends and prevents percussive force frompenetrating deeper as the fabric structure becomes more porous. Inanother embodiment, the auxetic yarn can have a different structure orchemistry that causes the yarn to become thicker as it extends whenunder tension. In yet another embodiment, the fabric layer can be atextile with loops of cotton yarn woven in such a way as to form 1 inchloops (or any size of loops from 0.1 inch to several feet) that areconnected with yarns of a lower modulus such that under percussive forceand the resulting extension will break and allow the fabric to expandbefore breaking again. In another embodiment the fabric layer can useloose weaves that take a zig-zag or other pattern that allows expansion.

In another embodiment, the layer can be a plate composed of one or moretypes combinations of the Bingham plastic, rubbery elastic plastic orfoam plastics of other embodiments disclosed herein and arranged in afish-scale pattern. In another embodiment, the plates overlap in otherpatterns. For example, the plates can be arranged such that the platesare contiguous and butt against each other. The plates can be arrangedsuch that the plates are non-contiguous and are placed so as to optimizeor improve the interaction with an impacting force. The textile can alsobe an ordinary textile.

In some cases above, this disclosure reference electronic components.Embodiments within the scope of the present disclosure that can be partof any electrical component may also include tangible and/ornon-transitory computer-readable storage media for carrying or havingcomputer-executable instructions or data structures stored thereon.Computing devices that may be used include the basic computer componentssuch as a processor, a bus, input/output mechanisms, a transmissionsystem including a transmission and/or receiving antenna, and so forth.Non-transitory computer-readable storage media or computer-readablestorage devices can be any available media that can be accessed by ageneral purpose or special purpose computer, including the functionaldesign of any special purpose processor as discussed above. By way ofexample, and not limitation, such non-transitory computer-readable mediacan include RAM, ROM, EEPROM, CD-ROM or other optical disk storage,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to carry or store desired program code means inthe form of computer-executable instructions, data structures, orprocessor chip design. When information is transferred or provided overa network or another communications connection (either hardwired,wireless, or combination thereof) to a computer, the computer properlyviews the connection as a computer-readable medium. Thus, any suchconnection is properly termed a computer-readable medium. Combinationsof the above should also be included within the scope of thecomputer-readable media.

Computer-executable instructions include, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. Computer-executable instructions also includeprogram modules that are executed by computers in stand-alone or networkenvironments. Generally, program modules include routines, programs,components, data structures, objects, and the functions inherent in thedesign of special-purpose processors, etc. that perform particular tasksor implement particular abstract data types. Computer-executableinstructions, associated data structures, and program modules representexamples of the program code means for executing steps of the methodsdisclosed herein. The particular sequence of such executableinstructions or associated data structures represents examples ofcorresponding acts for implementing the functions described in suchsteps.

Those of skill in the art will appreciate that other embodiments of thedisclosure may be practiced in network computing environments with manytypes of computer system configurations, including personal computers,hand-held devices, multi-processor systems, microprocessor-based orprogrammable consumer electronics, network PCs, minicomputers, mainframecomputers, and the like. Embodiments may also be practiced indistributed computing environments where tasks are performed by localand remote processing devices that are linked (either by hardwiredlinks, wireless links, or by a combination thereof) through acommunications network. In a distributed computing environment, programmodules may be located in both local and remote memory storage devices.

The various embodiments described above are provided by way ofillustration only and should not be construed to limit the scope of thedisclosure. Those skilled in the art will readily recognize variousmodifications and changes that may be made to the principles describedherein without following the example embodiments and applicationsillustrated and described herein, and without departing from the spiritand scope of the disclosure.

We claim:
 1. A helmet comprising: a shell; a plastic that changes from asolid to a liquid at an impact above a shear threshold, wherein theplastic is created by mixing water, vinyl alcohol, sodium tetraborateand fibers to yield a mixture that is stirred into a homogeneousgel-like substance that hardens into the solid; and a container thatstores the plastic, wherein the container is attached to an exteriorsurface of the shell.
 2. The helmet of claim 1, wherein the container isan air-tight container.
 3. The helmet of claim 1, wherein the fibers inthe plastic are mixed therein in different directions.
 4. The helmet ofclaim 3, wherein the plastic has intermixed therein fibers and each ofthe fibers is between 0.5-5 cm long.
 5. The helmet of claim 3, whereinthe plastic comprises a 4% polyvinyl alcohol and 2% sodium tetraborate.6. The helmet of claim 3, wherein the fibers are one of natural fibers,synthetic fibers and a combination of natural and synthetic fibers. 7.The helmet of claim 6, wherein, when the fibers are natural fibers, thenatural fibers comprise jute fibers.
 8. The helmet of claim 6, wherein,when the fibers are synthetic fibers, the synthetic fibers comprisepolyethylene terephthalate fibers.
 9. The helmet of claim 1, wherein theplastic comprises a first plastic in a first layer and the insertfurther comprises a second plastic in a second layer of the insert, thesecond plastic changing from a solid to a liquid at the shear threshold.10. The helmet of claim 1, wherein the plastic comprises between 2% and20% of hydrolyzed polyvinyl alcohol and between 0.5 and 8% borate.
 11. Ahelmet pad comprising: a container; and a plastic contained within thecontainer, the plastic comprising a layer that changes from a solid to aliquid at an impact threshold, wherein the container containing theplastic is attached to an exterior surface of a shell of a helmet andwherein the plastic is created by mixing water, vinyl alcohol, sodiumtetraborate and fibers to yield a mixture that is stirred into ahomogeneous gel-like substance that hardens into the solid.
 12. Thehelmet pad of claim 11, wherein the fibers in the plastic are mixedtherein in different directions.
 13. The helmet of claim 1, wherein theplastic is in a first plastic layer and wherein the shear threshold is afirst shear threshold, the helmet further comprising: a second plasticthat changes from a solid to a liquid at an impact above a second shearthreshold, wherein: the second plastic is created by mixing water, vinylalcohol, sodium tetraborate and fibers to yield a mixture that isstirred into a homogeneous gel-like substance that hardens into thesolid; the second plastic is within a second plastic layer; the firstshear threshold differs from the second shear threshold based ondifferent percentages of the sodium tetraborate in the first plasticlayer and the second plastic layer; and the container stores the firstplastic layer and the second plastic layer.